Gravity mixer

ABSTRACT

A gravity mixing machine for free-flowing products in which a mixing drum is arranged inclined to the horizontal and rotatable about its longitudinal axis and into which the material is introduced at its higher end and discharged at its lower end. The drum is divided into a plurality of successive mixing chambers by the provision of radially extending plates.

United States atent 1151 3,666,240 Lodige et al. [451 May 30, 1972 GRAVITY NIIXER 2,582,365 l/l952 Westphal ,....165/89 X [72] Inventors: Wilhelm Lodige; Fritz Lodige; Joseph ggg gg 11/1953 X Lucke; Karlheinz Luke, all of Paderborn, 4 H1960 swims /3 x German 3,216,345 11/1965 Rigby et al.. ....259/3 X 3,355,817 12/1967 Birk ..165/89 X [73] Assignee: said Wilhelm Lodige, Fritz Lodige and Josef Lucke, all of Paderborn, Germany; FOREIGN PATENTS OR APPLICATIONS by Sam Karlhemz Luke 1,227,872 3/1960 France .259/3 [22] Filed: Apr. 29, 1969 1,300,065 6/1962 France ....259/3 372 046 /1932 Great Britain..... ....259/3 1. 2 ,266 [211 App No 8 0 556,942 /1943 Great Britain ..259/3 Foreign Application Priority Data Primary Examiner-Edward L. Roberts May 14. 1968 Germany P 17 57 478.6

Attorney-McNenny, Farrington, Peame & Gordon [52] US. Cl ..259/3, 259/58 {51] 1111. c1 ..B0lf 9/06, BOlf 15/06 ABSTRACT [58] Field of Search ..259/DIG. 18, 3,14, 30, 57, A 1

gravity mixing machine for free-flowing products 1n WhlCh a 259/81 165/109 89 mixing drum is arranged inclined to the horizontal and rotata- 5 6 R f d ble about its longitudinal axis and into which the material is in- 1 e erences e troduced at its higher end and discharged at its lower end. The UNITED STATES PATENTS drum is divided into a plurality of successive mixing chambers by the provision of radially extending plates. 1,056,974 3/1913 Conway ..259/57 X 2,310,603 2/1943 Taylor ..259/3 9 Claims, 3 Drawing Figures GRAVITY MIXER BACKGROUND OF THE INVENTION It is known that particularly fragile materials which are not intended to undergo any intergranular destruction can be mixed in free-fall or gravity mixers, such as double-cone mixers. In such mixers it is only possible to adequately mix a batch by using very long mixing times. With certain materials which have a wide range of granule size and weight, these conventional mixers have even been known to promote disintegration. They are totally unsuitable for use as flow mixers.

SUMMARY OF THE INVENTION It is an object of the invention to provide a gravity mixer by means of which even highly sensitive free-flowing materials with a wide grain size distribution can be mixed quickly, intensively and uniformly without sufi'ering any damage in continuous operation.

To achieve this object, there is provided a gravity mixer for free-flowing materials, the mixer comprising:

a longitudinally extending mixing drum rotatable about a longitudinal axis inclined to the horizontal, and having an upper end, a lower end, and a drum wall running between said upper end and said lower end,

a plurality of radially extending plates disposed in the drum in such a way as to divide the drum into a plurality of successive intercommunicating chambers, said chambers being adapted for said material to flow successively through each of said chambers to the lower end of the drum; and

means for discharging said material from the lower end of the mixing drum.

The mixing chambers communicate with one another in such a way that the material to be mixed is delivered gradually from the first, uppermost mixing chamber through each of the following lower mixing chambers to the outlet situated at the lower end and at the same time undergoes constant gentle mixing.

The mixer is a gravity mixer which does not contain any moving mixing tools and which unlike conventional gravity mixers does not function as a batch mixer, but only as a flow or continuous mixer. It is advantageously provided with a cylindrical drum which has a feed opening in one of its end walls and a discharge opening or outlet in the other.

To ensure that the material to be mixed is kept in motion inside the mixing vessel from the feed opening to the outlet, the mixing vessel is preferably inclined at an angle of from to 25 to the horizontal. It is designed to rotate at such a speed that the material being mixed is not subjected to any centrifugal forces of sufficient magnitude to impede the downward trickling of the material being mixed. To this end, a drum with an internal diameter of 400 cm is advantageously driven at 10 to 30 r.p.m.

In the case of a mixing vessel with a cylindrical drum, the required intensive mixing effect is achieved by dividing up the drum with circular plates whose outer diameter corresponds to the internal diameter of the mixing vessel. Where the mixing vessel is rectangular or polygonal, the plates must have an external shape which corresponds to the shape of the vessel. The internal diameter of the circular plate is to between 50 percent and 80 percent of the drum diameter, depending upon the free-flow properties of the material to be mixed and the required throughput rate of the product. The segments are advantageously distributed over the entire length of the mixing vessel at intervals of from to 40 percent of the drum diameter. These mixing chambers should be equal in size apart from the first mixing chamber which can be wider.

Through the rotation of the mixing vessel the material to be mixed is kept continuously tumbling, trickling and flowing in each of the mixing chambers, a movement similar to that which occurs in conventional tumbling-barrel mixers. Due to the inclined arrangement of the mixing vessel and the continuous delivery of the material for mixing, the material in each mixing chambers merges with the material in a following lower mixing chamber and, together with the material already being mixed in that lower chamber immediately participates again in the tumbling, trickling and flowing movement. The greater the extent to which the mixing vessel is filled and the more steeply it is inclined, the larger the quantity of material flowing over in this way and the longer the flow path will be, i.e. some material can even merge into the next but one mixing chamber or even into the one after that.

To prevent heavier particles of the material being mixed from staying longer than lighter particles in the individual mixing chambers, each mixing chamber can be provided with a lifting or entraining plate advantageously of the same width and height as the chamber. When during rotation of the mixing vessel this entraining plate reaches the slope angle of the material being mixed, most of the heavier material still in front of the plate is displaced into the adjacent mixing chamber and some into the chamber after that, where it immediately participates in the mixing movement together with the material already present there. When the mixer is emptied, these plates ensure that even the last remaining fractions of the mixed material leave the mixer quickly through the outlet opening.

In order to obtain high levels of thoroughness in mixing, the mixing drum advantageously has a length equal to at least 4 times its diameter so that a number of small mixing chambers can be formed. In cases where the various components of the material to be mixed are continuously delivered, it is possible to satisfy even the most stringent requirements in regard to the thoroughness of the mixing. Even in cases where the materials to be mixed are delivered at timed intervals, adequate mixing results can be obtained even when the intervals are short.

The mixer is also eminently suitable for cooling or heating mixing stock. To this end, it is provided with a double jacket with inflow and outflow facilities, for example in the form of bores in the shaft and in spokes which support the drum of the mixing vessel. Compared with conventional mixers, cooling and heating are much more intensive in this mixer because this mixer is comparable with a radiator in so far as, in addition to the wall of the mixing vessel, the plates incorporated to divide the mixing vessel into small mixing chambers and the entraining plates in the mixing chambers also communicates the temperature of the cooling or heating medium to the material being mixed. In addition, there are no moving mixing tools to counteract cooling through friction with the material being mixed.

Other advantages and features of the invention will be apparent from the following description of the drawings and also from the claims.

DESCRIPTION OF THE DRAWINGS One embodiment of the invention is diagrammatically illustrated by way of example in the accompanying drawings, wherein:

FIG. 1 is a schematic vertical longitudinal section through the mixer as a whole.

FIG. 2 is a schematic cross-section of the mixing vessel on the line lIIl of FIG. 1, and

FIG. 3 is a schematic cross-section of the mixing vessel on the line III-lll of FIG. 1.

The mixer comprises a cylindrical drum mixing vessel 1 which at both ends is mounted on a shaft 2 by way of spokes 3. The shaft 2 is rotatably mounted inclined to the horizontal in bearings 4 in such a way that it cannot be axially displaced. The bearings 4 are in turn mounted in supports 5 and 5a situated at different levels.

The mixing vessel 1 is divided up into several small mixing chambers 7 by circular sheet-metal plates 6 which also serve as head pieces. From the inlet to the outlet the successive mixing chambers are situated progressively lower corresponding to the inclination of the drum so that providing the vessel is adequately filled the material to be mixed flows over from one mixing chamber to the next. In each mixing chamber there is an entraining plate 8 which, each time the mixing vessel 1 completes a revolution, takes with it even relatively heavy particles of the material being mixed and transfers them to the next mixing chamber. In addition, the plates also provide for the complete emptying of the mixing vessel at the end of mixing. In the embodiment shown in FIGS. 1 to 3, the plates 8 in successive chambers 7 are angularly displaced from one another by 90.

The shaft 2 is driven by a geared motor 9 through a chain drive 10 at a speed which does not produce a centrifugal force sufficient to interfere in any way with the free fall of the material being mixed.

An endless conveyor belt 11 is arranged above the mixer for loading it. Above the conveyor belt there are metering units K to P for the various components to be mixed which are preferably delivered continuously. The material falls off the conveyor belt 11 in the direction of arrows 11a and 11b through a hopper 12 which projects into the first mixing chamber of the mixing vessel 1 through a cover plate 13 fixed to the support 5. At the outlet end of the drum, a discharge funnel 14 is fixed to the support 50 so that the process of mixing can take place in the absence of any dust provided slip ring seals (not shown) are arranged between the cover plate 13 and discharge funnel 14 on the one hand and the rotating mixing vessel 1 on the other hand.

The wavy line 16 in FIG. 3 represents the surface of material being mixed trickling or sliding down at a certain angle with the mixing vessel 1 in rotation. The line 16a in FIG. 1 with the arrows 16b pointing downwards denotes the material continuously flowing over from one mixing chamber to the next in the axial direction. In the vicinity of the long arrow 17 in FIG. 3 the material to be mixed does not move in bulk although it is continuously lifted by the rotating mixing vessel 1 in a kind of tumbling movement up to a reversing point 17a. From the reversing point 170, the material to be mixed trickles downwards in the vicinity of the arrows 18 along and below the wavy line 16, as in free fall, at the same time in a stream of mixed material moving in the direction of the line 16a and the arrows 1617 which is continuously subjected to a kind of rolling motion.

The arrows 18 in FIG. 1 indicate that some of the material trickling or falling down from the reversing point 17a remains in the same mixing chamber while some flows into the next mixing chamber and even into the one after that, together with the stream of mixed material flowing towards the outlet end of the mixing vessel 1.

Throughout the whole length of the mixing vessel 1, the material to be mixed, coming from different directions and moving in different directions is inevitably subjected in each mixing chamber 7 to the tumbling, trickling, rolling and flowing motion.

To enable the mixer to be additionally used for cooling or heating feed stock, the mixing vessel 1 is provided with a double wall jacket 19 in the embodiment shown. To enable heating or cooling media to be introduced into and carried away from this double wall jacket 19, the ends 2a and 2b of the shaft 2 and the spokes 3 are made hollow. The temperature of the heating or cooling medium is communicated to the feed stock not only by the wall of the mixing vessel 1 but also by the circular plates 6 and the entraining plates 8.

It will be understood that the invention is not to be limited to the exact construction shown and described but that various changes and modifications may be made without departing from the spirit and scope of the invention, as defined in the appended claims.

We claim:

1. A gravity mixer for free-flowing materials, the mixer comprising:

a longitudinally extending mixing drum rotatable about an inclined longitudinal axis inclined to the horizontal, and having an upper end, a lower end, and a drum wall running between said upper end and said lower end;

a plurality of axially spaced, radially inwardly extending, an-

nular plates having a central aperture therein and disposed in the drum in such a way as to divide the drum into a plurality of successive intercommunicating chambers, said chambers being adapted for said material to flow successively through each of said chambers to the lower end of the drum;

at least one entraining plate in each chamber radially inwardly projecting from the drum wall a distance no greater than the radial distance from the drum wall to the aperture and extending between successive chamberforming plates, the entraining plates in successive chambers being angularly displaced; and

means for discharging said material from the lower end of the mixing drum.

2. A mixer as claimed in claim 1 wherein the apertures are circular and each aperture has an internal diameter of from 50 to percent of the diameter of the mixing drum.

3. A mixer as claimed in claim 2 wherein the radially extending plates are arranged in the mixing vessel at intervals of from 15 to 40 percent of the diameter of the mixing drum.

4. A mixer as claimed in claim 1 comprising a driven shaft inclined at an angle of from 10 to 25, for supporting and rotating the mixer.

5. A mixer as claimed in claim 4, comprising radial spokes extending from the driven shaft and supporting the wall of the drum.

6. A mixer as claimed in claim 5, further comprising bores disposed longitudinally in the spokes and the shaft for flow of cooling or heating medium.

7. A mixer as claimed in claim I, further comprising a double wall jacket surrounding the mixing drum for accommodating a cooling or heating medium.

8. A mixer as claimed in claim 7, further comprising means for circulating the heating or cooling medium in the double wall jacket.

9. A mixer as claimed in claim 1 wherein the two ends of the mixing vessel are provided with fixed dust-tight feed and discharge funnels. 

1. A gravity mixer for free-flowing materials, the mixer comprising: a longitudinally extending mixing drum rotatable about an inclined longitudinal axis inclined to the horizontal, and having an upper end, a lower end, and a drum wall running between said upper end and said lower end; a plurality of axially spaced, radially inwardly extending, annular plates having a central aperture therein and disposed in the drum in such a way as to divide the drum into a plurality of successive intercommunicating chambers, said chambers being adapted for said material to flow successively through each of said chambers to the lower end of the drum; at least one entraining plate in each chamber radially inwardly projecting from the drum wall a distance no greater than the radial distance from the drum wall to the aperture and extending between successive chamber-forming plates, the entraining plates in successive chambers being angularly displaced; and means for discharging said material from the lower end of the mixing drum.
 2. A mixer as claimed in claim 1 wherein the apertures are circular and each aperture has an internal diameter of from 50 to 80 percent of the diameter of the mixing drum.
 3. A mixer as claimed in claim 2 wherein the radially extending plates are arranged in the mixing vessel at intervals of from 15 to 40 percent of the diameter of the mixing drum.
 4. A mixer as claimed in claim 1 comprising a driven shaft inclined at an angle of from 10* to 25*, for supporting and rotating the mixer.
 5. A mixer as claimed in claim 4, comprising radial spokes extending from the driven shaft and supporting the wall of the drum.
 6. A mixer as claimed in claim 5, further comprising bores disposed longitudinally in the spokes and the shaft for flow of cooling or heating medium.
 7. A mixer as claimed in claim 1, further comprising a double wall jacket surrounding the mixing drum for accommodating a cooling or heating medium.
 8. A mixer as claimed in claim 7, further comprising means for circulating the heating or cooling medium in the double wall jacket.
 9. A mixer as claimed in claim 1 wherein the two ends of the mixing vessel are provided with fixed dust-tight feed and discharge funnels. 